Emboli form, for example, as a result of the presence of particulate matter in the bloodstream. Vascular emboli are a major single causative agent for multiple human pathologies. It is a leading cause of disability and death. Clots or thrombi that become dislodged from the point of origin are termed emboli.
Such particulate matter may originate from a blood clot occurring in the heart. It may be a foreign body, but may also be derived from body tissues. For example, atherosclerosis, or hardening of the blood vessels from fatty and calcified deposits, may cause particulate emboli to form. Moreover, clots can form on the luminal surface of the atheroma, as platelets, fibrin, red blood cells and activated clotting factors may adhere to the surface of blood vessels to form a clot.
Blood clots or thrombi may also form in the veins of subjects who are immobilized, particularly in the legs of bedridden or other immobilized patients. These clots may then travel in the bloodstream, potentially to the arteries of the lungs, leading to a common, often-deadly disease called ‘pulmonary embolus’. Thrombus formation, and subsequent movement to form an embolus, may occur in the heart or other parts of the arterial system, causing acute reduction of blood supply and hence ischemia. The ischemic damage often leads to tissue necrosis of organs such as the kidneys, retina, bowel, heart, limbs, brain or other organs, or even death.
Since emboli are typically particulate in nature, various types of filters have been proposed in an attempt to remove or divert such particles from the bloodstream before they can cause damage to bodily tissues.
For example, U.S. Pat. No. 6,258,120 discloses a filter device intended to be inserted into the artery of a patient. However, the device has an inherent drawback, which is that the actual trapping of an embolus, for successful operation of the device, may result in blockage of blood flow through the device and hence through the artery. Other disclosed embodiments of the device, which may not be blocked by clots, are not able to filter clots, and may in fact funnel such particulate matter to the blood vessels leading to the brain. None of the disclosed embodiments of the device is anchored to the artery, but instead rely upon conformation to the arterial shape and size to maintain the position of the device, which is not secure. In view of the natural force of blood pressure and elastic recoil of the arterial wall, proper placement and control of position of the device are of paramount importance. If the device moves even slightly, it may even block the artery which it is intended to protect. Such movement may be caused by blood flow for example, as the blood pulse moves through the artery.
U.S. Pat. Nos. 4,873,978, 5,814,064, 5,800,457, 5,769,816, and 5,827,324 describe devices that are intended only for temporary insertion into a blood vessel. Therefore, these devices avoid the difficult issue of simultaneously successfully filtering emboli while also maintaining blood flow through the blood vessel. As such, they do not address the problem of prolonged filtration of the blood.
U.S. Pat. No. 5,234,458 appears to disclose a filter device that is intended to be left in the vessel for a period of time. However, the disclosed filter device lacks a tapered shape, thus introduction and positioning may be unsafe and complex. Such a device does not feature a sufficiently strong anchoring system and the filter does not include a mesh.
The lack of a suitable anchoring system is a general problem with devices disclosed in the background art, as the pulsating blood flow, aortic elasticity and movement may all cause a device inserted into a major blood vessel to become dislodged. Furthermore, those devices which feature rigid structures may create turbulent blood flow at certain locations such as the aortic arch, leading to decreased cerebral blood flow and possible activation of the clotting mechanism.
Therefore, there is a need for a more effective and safer device and method for protecting against particulate such as emboli.